Please help me!!!

[1843]

hi to all,
I built HH opt2 :
Q11 is warm-up and r41 influence in working the HH
What is my wrong?:confused:

[Pilot68]

Impdedance of earphone low?

Hi,

what' the impedance of your earphone, i think 8 Ohm is could heat up Q11 and R41!

Usually standard earphones hve 32 Ohm i guess...

wish you success...

Jörg

[1843]

hi Jorg
tank you for reply,
I am using a small (8 OHM) speaker
My hh(opt2) has some erors:
When volume is down, it detecs anything such as air! and when volume is max, it works corrctly but Q11 will be hot.
R41 doesn't work correctly and it influence in HH working :confused:

[1843]

dear carl

hi dear carl,What is my wrong?

[Reg]

Hi 1843,

It is possible that R 41 or R 35 or both could influence how the HH works. This is especially true if you are using batteries such as AA types. The reason is the HH will draw too much current each audio pulse and this will influence the transmit pulse because the voltage is dropping. You should be able to see this happen by monitoring the 12V with a scope.

Using a heavier battery helps, but the best solution is to use a couple of extra 1.5V AA batteries in series with the original 12V and then regulate the voltage to 12V using a simple regulator such as a LM7912.

A regulator will help reduce some of the problems.

Using a good set of high impedance headphones and keeping the volume low will help a lot because then the audio will not draw nearly as much current, so there will be less voltage variation. Using it this way will cause the detector to be much more stable.

PI detectors are very touchy and any variation in the power supply will cause the transmit pulse to vary. This will cause or appear as instability or loss of sensitivity.

Hope this helps.

Reg

[1843]

Hi REG!
Thank you very much for your help!

[1843]

best setings

Hi to all
I haven't scope for test..
What is the values of R2, R45, R46, R31 & R35 for maximum depth?:o

[Carl-NC]

Sorry, missed this... did you get it fixed?

[1843]

Hi to all

I have a problem:
When I moving the coil to the up & down (almost 10cm) near the ground, HH make noising.
What is the wrong???:confused:

[Reg]

Hi 1843,

There is nothing wrong if your PI responds to the ground mineralization, especially if the delay is less than about 20 usec. This is normal.

If you have not Faraday shielded the coil, the PI will respond with a stronger signal than if it is shielded. So, it is necessary to shield the coil to reduce this ground effect.

However, even with a Faraday shield on the coil, if the delay is adjusted to a very short delay time, such as a delay of 15 usec, the PI will detect the ground as a target, and this can produce a signal. This intensitity of the detection of the ground will depend a lot on the type of soil also. Pure sand will usually produce a very weak signal if any, while a clay based soil will generally cause a strong response. So, this signal caused by the ground can vary from area to area and depends upon the ground conditions.

Reg

[1843]

Hi Reg
Thank you for early reply!
I have a Faraday shilded coil (10" Carls coil).
I can't regulate the pulse pots, Please tell me the fixed values of R42, R45 & R46 for best revenue

[Reg]

Hi 1843,

It is difficult to say what is the best settings because it depends upon a lot of factors such as what you want to hunt, what the ground conditions are and just how the HH works.

As a general rule, you could start out with the following settings and try different ones from there.

R 42, sets the main sample delay. You should set this for the shortest time possible (the resistance value near 0 ohms) and have the detector work ok for the maximum sensitivity. However, any time shorter than about 20 usec will cause more and more ground response, which could make searching more difficult.

Don't be surprised if the detector appears to not work or not work correctly if this setting is too short (the resistance close to 0). It is not uncommon to not be able to get a coil to work at less than 20 usec. So, you could start with a minimum resistance setting and slowly increase the resistance until the detector suddenly appears to start working ok. This should be the point where you have the maximum sensitivity. Once you find this setting, you might want to add just a little extra resistance, but not much. This will assure the detector will work once everything gets hot.

R 45 sets the secondary delay. This setting isn't that critical and could be set mid position to start. If this setting is set at minimum (0 resistance), there might be some minor sensitivity loss, but in most cases, it is possible that it wouldn't be noticed. This setting has a greater effect on iron, silver and copper objects.

R 46 sets the sample widths and adjusts from about 3 usec to 50 usec. A good place to start is to set this control at mid position or maybe a little less. If this setting is too short or too long, there will be some depth loss, depending upon what you are trying to detect. If you are trying to detect gold objects, then I prefer a setting of about 10 usec, which would be somewhat close to minimum setting, maybe 2K to 3K as a value to start. This setting is more of a preference but does affect the noise level as well as the sensitivity. Detecting iron objects could use a little longer time, but not much.

One thing you could do is to start at mid position and slowly reduce the setting while checking the sensitivity to an object. Once the adjustment begins to cause a depth loss, then increase the setting slightly and try that setting initially.

In any case, do not be afraid of experimenting with different settings to see how they affect the operations of the detector. The more you experiment, the more you will learn just what each control does as well as what is the best setting for your applications.

I hope this helps.

Reg

[1843]

Carl & Reg

Hi
I use a 12v regulator & a high impedance headphone for my HH.
But it hadn't better effect in any problems.
When I turn up the volume maximum, HH works with nothing problem & ground not effect in HH working, But Q11 will become very hot!
Please solve my problem.
Thanks a lot

[Unregistered]

----

New opt . 2 not work fine. Older is fine.

[Reg]

Hi 1843,

Try turing the threshold adjustment down so you don't hear any sound and then check to see if Q 11 is still getting hot. If it is, then something is obviously wrong. It could be that Q11 is bad, or part of the previous circuit isn't correct.

Double check all transistors to make sure they are the correct number and are installed correctly. The most logical error would be that one of the transistors is incorrect, defective, or installed wrong. Also, look for any possible solder bridges between parts of the circuit in that area. The design will work fine if everything is correct.

Reg